Many times it is desired to control the average current through an electrical load so as to ensure the proper operation of the electrical load. For electrical loads such as the inductance coil of a solenoid relay, many prior circuits have controlled average current through the solenoid inductance by alternately turning on and off a switching device connected in series with the solenoid inductance. This preferred technique minimizes power dissipation by avoiding operating the control device in a linear mode since the control device is operated in a switching mode. Typically, the current through the solenoid inductance is sensed and the switching device is turned on when the solenoid current is below a certain level and turned off when the solenoid current exceeds a certain level. In this manner, the solenoid current will oscillate repetitively between maximum and minimum levels and thereby a desired average current level is achieved. Examples of such prior art solenoid current control systems are shown in U.S. Pat. Nos. 4,764,840, 4,300,508, 4,729,056, 4,736,267, and 4,680,667. Some of these prior systems utilize separate high and low current threshold comparators to accurately control the maximum and minimum load current levels.
Prior high and low comparator systems, such as those noted above, are subject to generating undesired or false turn-on and turn-off signals which are coupled to the switching device. This is because of noise which corrupts a load current sense signal provided to the high and low current threshold comparators. Thus, undesired or false switching of the switching device or the circuitry which generates the current control signal provided to the switching device can occur. This can disrupt the maintaining of a desired average current in the solenoid inductance.